Worldbin: Space Travel.

(Sorry for the gap – I was in Scotland. Nice place, wide open skies and blisteringly cold, but no internet)

Space, as I have already said before, is big. And because it is so big, when you travel across it, you have to go into ludicrous speeds in order to get anywhere anytime soon. Here’s a few real-world projects that have been floated about how to accelerate stuff in a vacuum.

Ion Drives

An ion drive (also called an ion thruster) is quite simple. Space is not empty – it has about 1 atoms/cm3 (this can rise to 1000 atoms/cm3 in gas clouds, however), normally in the form of Hydron nuclei – protons. Your ship fires these backwards via electrostatic or electromagnetic force, and Newton III means you accelerate because of this. Now, the speeds at which you accelerate are very, very small. However, the energy needed to use the drive is also very, very small, and can easily be powered by solar cells. It is a lot more effective on smaller craft, like probes, as you can have a body that is mostly ion drive. But for larger ships, you need to factor in things like living quarters and air recycling. Also it will take years to get up to any decent speeds, which is not useful for crewed missions. However, as it accelerates, it will move quicker, and cover more space, so fire more protons, and so move quicker still. That’s nice. Also, to slow down – just reverse the polarity of the neutron flow electric field.

Railguns

Yes, you read that right, railguns. Now, I hear you cry, how can a railgun launch ships into space? The atmosphere is too thick and too turbulent to launch from Earth, and without a space elevator, how could we construct one in space? Both are realistic points. Without power beaming, carbon nanotubes and batteries a magnitude more efficient, we cannot have a railgun in space. But we can have one on the ground, as long as we sort out the atmosphere first. Now, I’m not talking about pseudo-scientific weather magic, nor putting the railgun on Mount Everest. All you need is magnetised ice. Ice itself is not magnetic, but if you add iron filings to the water as it congeals, then you can accelerate it in a magnetic field. To launch someone, you will need quite a few megaton, maybe even gigaton, blocks of this ice, as well as your ship. (NB- the ice blocks must be larger in size than the ship, otherwise this will not work at all)

You get a long railgun – several km in length, and in quick succession (and I do mean quick), you fire your ice blocks, then the ship. As the ice hits the atmosphere, it will “burn up” and release high-energy, high-pressure water vapour into the atmosphere in a trail behind it, like a comet. This will mean there will be a low-pressure “tube” where the ice has passed. The second block will go further than the first, as it has less atmosphere in the way, and will extend this “tube”, as well as dropping the pressure of the original tube. As this goes on, you should create a low-pressure, stable area where you can fire you ship. If you time it right, the “tube” should start to collapse at about the time when the next ice block moves through it to stabilise it. But when the ships passes through the near-vacuum, it will collapse behind it, propelling it forwards, and accelerating it further.

The big downside to this, however, is that when the “tube” collapses, there will be some atmospheric fallout because of it. For example, the shockwave. This will deafen anyone without ear protection in a 20km radius, and flatten anything within 5km. All free-standing structures (i.e. everything that isn’t a bunker of 1 storey tall) in about 10km will be destroyed. Then there will be the second shockwave, as the atmosphere rushes backwards, which will do the whole thing over again. Yay. Also – the weather. If you’ve ever seen one of those super-storm things on the TV, you will now be able to see it in real life. And the atmosphere will be exceptionally ionized, due to the passing of the charged ice, meaning that there will be al lot of lightning. So really, this thing is only viable in the desert, where everything is tightly tied down. But still – think of the speeds you would obtain!

Project Orion

This is actually an older idea, first mooted back in 1946. However, you may know it by another name – nuclear propulsion. (Un?)Fortunately, the Partial Nuclear Test Ban Treaty (or, to give it it’s full name the “Treaty banning Nuclear Weapon Tests In The Atmosphere, In Outer Space And Under Water”) means that it will never get off the ground. The idea behind it is very simple.

1. Construct a large ship (most likely a colony ship) in Low Earth Orbit, with a large dish at it’s rear that could collect the energy.

You see, nuclear bombs no not need oxygen to work. Only the critical mass. The energy released would propel the ships forwards as it landed on the collecting dish, which it could then use.

The downside to this is that there would be some serious fallout. As in nuclear fallout. The amount of it, and the danger it would pose, would be determined by how far the ship was away from Earth, in which direction it was facing, and how powerful the bombs would be. The “ideal” situation would be when you spend 6 months moving the ship away from Earth, and then hit the big red button. The EMP would do minimal damage, as Earth would be shielded by the Sun, and the fallout should have dissipated and decayed enough to be safe by the next time Earth came around.

So, in summary;

Ion Drives – clean energy for probes to hit c and to boldly go where no man has gone before.

Railguns – launch small crews to Europa, but destroy the surrounding countryside.

Nuclear Propulsion – get rid of the excess nuclear stockpile in order to launch generation ships to Proxima Centauri.